Tizard mission Letter from E G Bowen, 11 September 1940. E G Bowen, the head of the airborne radar team, wrote to Hanbury Brown while en route to Washington, DC, USA, where he joined the 'Tizard Mission'. Tizard's mission was to secure British-American collaboration on air defence, starting with disclosure of British secrets in return for help on technical and production problems. 1940